OBR conducts scrutiny and analysis of HM Treasury’s costing of tax and welfare spending measures. During the run-up to the Budget and the Spring Statement, the OBR subjects the Government's draft costings of tax and spending measures to detailed challenge and scrutiny. These are then stated in the EFO and the Treasury's policy costing documents with the OBR stating whether it endorses the costings that the Government finally publishes as reasonable central estimates. The OBR also assigns each certified costing with an uncertainty rating based on data quality, modelling and behavioural response. In March 2014, the OBR has published a briefing paper describing its role in policy costings and how they fit into the forecast process. Assess the long-term sustainability of the public finances The OBR also assesses the long-term sustainability of the public finances. Its annual Fiscal sustainability report sets out long-term projections for different categories of spending, revenue and financial transactions and assesses whether they imply a sustainable path for public sector debt. The Fiscal sustainability report also analyses the health of the public sector's balance sheet using both conventional National Accounts measures and the Whole of Government Accounts as prepared using commercial accounting principles. In October 2015 the UK Parliament approved a revised Charter for Budget Responsibility that required the OBR to produce a fiscal risks report at least once every two years and the Government to respond to it formally within a year of publication. In July 2017, OBR published a review of risks from the economy and financial system, to tax revenues, public spending and the balance sheet, and included a fiscal stress test. Additional functions Devolved tax and spending forecasts In addition to these core responsibilities, the Government asked the OBR to forecast the Scottish receipts for four taxes that were devolved to the Scottish Government from April 2015 onwards; the Scottish rate of income tax, stamp duty land tax, landfill tax and the aggregates levy. Following the passing of the Scotland Act 2016, the OBR also forecast Scottish air passenger duty and aspects of Scottish social security that will be devolved. The OBR has published these forecasts since March 2012 alongside UK revenue forecasts. The OBR has a reciprocal statutory duty of cooperation with the Scottish Fiscal Commission in the production of forecasts of devolved Scottish taxes and welfare expenditure. In a Command Paper published with the Wales Bill 2014, the Government requested